To quote from an analysis of the flick by Dr. Jeff Masters, Chief Meteorologist for the Weather Underground:
Hurricanes and severe weather
The biggest failure in the movie's presentation of science comes in the discussion hurricanes and severe weather events. The devastation wrought by Katrina is used to very dramatic effect to warn of the dangers climate change presents. We are told that Katrina grew "stronger and stronger and stronger" as it passed over the warm waters of the Gulf of Mexico that were heated up by global warming.
We are told that global warming is increasing the intensity of hurricanes, but not provided information on the great amount of uncertainty and vigorous scientific debate on this issue. Graphs showing recent record insurance losses from natural disasters are presented, but no mention is made of how increasing population and insistence on building in vulnerable areas are the predominant factors causing recent high insurance claims from disasters such as Katrina.
Gore points to some unprecedented events in 2004 as evidence of increasing severe weather events worldwide--the record 10 typhoons in Japan, the most tornadoes ever in the U.S., and the appearance of Brazil's first hurricane ever. However, examples of this kind are meaningless. No single weather event, or unconnected series of severe weather events such as Gore presents, are indicative of climate change.
In particular, the IPCC has not found any evidence that climate change has increased tornado frequency, or is likely to. Gore doesn't mention the unusually quiet tornado season of 2005, when for the first time ever, no tornadoes were reported in Oklahoma in the month of May.
Turns out NOAA studies suggest just the opposite is likely to happen. And for the very same reason these past hurricane seasons have proven to be a media bust. Because of the wind shears, inhibiting the hurricanes' growth.
Following in the footsteps of an earlier study, government scientists on Tuesday said warmer oceans should translate to fewer Atlantic hurricanes striking the United States.
"Using data extending back to the middle 19th century, we found a gentle decrease in the trend of U.S. landfalling hurricanes when the global ocean is warmed up," Chunzai Wang, a physical oceanographer and climate scientist with NOAA's Atlantic Oceanographic and Meteorological Laboratory in Miami, said in a prepared statement.
The study found that the warming of the Pacific and Indian oceans plays an important role in determining hurricane activity in the Atlantic.
A study released in December found that as the Atlantic basin becomes hotter, hurricane intensity likely won't increase and might even deflate somewhat. That study found that ocean's heat acts to stabilize the upper atmosphere, which, in turn, hurts a storm's ability to build.
Regarding the most recent study, Wang said vertical wind shear is not the only factor that determines Atlantic hurricane activity, but noted it is an important one. Other factors include atmospheric humidity, sea level pressure, and sea surface temperature, he said.
Observations from 1854 to 2006 show almost all the world's oceans have warmed, particularly in large areas of the tropical regions of the Pacific, Atlantic, and Indian oceans, the study found. That warming has increased vertical wind shear in the Atlantic and suppressed hurricane activity, the NOAA study found.